On Mon, Sep 29, 2008 at 06:42:20AM -0700, Arjan van de Ven wrote:
...
> > This patch changes that behavior of the device driver so it uses
> > uncacheable instead of cacheable mappings. This is the only thing
> > I'm uncertain about for this patch.
>
> ioremap() also is uncachable today.
Ok...it was using cacheable mapping on ia64 until this commit in 2007:
http://www.gelato.unsw.edu.au/archives/linux-ia64/0703/20211.html
I stopped paying close attention on ia64 in 2006 for the most part.
It's always been uncacheable on parisc.
After finding willy's patch (March 2006) on lwn.net, I remember the
discussion around changing the behavior of ioremap() to be uncached:
http://lwn.net/Articles/178084/
And I have to agree with willy/alan, pci_iomap() is already doing this.
However, pci_iomap() isn't quite right either:
if (flags & IORESOURCE_MEM) {
if (flags & IORESOURCE_CACHEABLE)
return ioremap(start, len);
return ioremap_nocache(start, len);
}
I expect it needs to use ioremap_cache() instead of ioremap().
One line patch below fixes that. Build-tested on x86 only.
Signed-off-by: Grant Grundler <grundler@xxxxxxxxxxxxxxxx>
> > And I have a second issue less important issue.
> > What is the result of ioremap_pcibar(pci, 1) when BAR0 is a 64-bit
> > bar? Given the name, I expect to call "ioremap_pcibar(pci,2)" to get
> > the desired result. Maybe just document how to handle this correctly
> > in Documentation/pci.txt would be sufficient.
>
> we should detect this and DTRT inside the implementation, not in the
> drivers.
pci_iomap() is already doing this. See lib/iomap.c:pci_iomap().
thanks,
grant
diff --git a/lib/iomap.c b/lib/iomap.c
index d322293..5565cf9 100644
--- a/lib/iomap.c
+++ b/lib/iomap.c
@@ -267,7 +267,7 @@ void __iomem *pci_iomap(struct pci_dev *dev, int bar, unsigned long maxlen)
return ioport_map(start, len);
if (flags & IORESOURCE_MEM) {
if (flags & IORESOURCE_CACHEABLE)
- return ioremap(start, len);
+ return ioremap_cache(start, len);
return ioremap_nocache(start, len);
}
/* What? */
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